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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2007 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.4"></a>
<span class="sourceLineNo">005</span> * you may not use this file except in compliance with the License.<a name="line.5"></a>
<span class="sourceLineNo">006</span> * You may obtain a copy of the License at<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * Unless required by applicable law or agreed to in writing, software<a name="line.10"></a>
<span class="sourceLineNo">011</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.11"></a>
<span class="sourceLineNo">012</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.12"></a>
<span class="sourceLineNo">013</span> * See the License for the specific language governing permissions and<a name="line.13"></a>
<span class="sourceLineNo">014</span> * limitations under the License.<a name="line.14"></a>
<span class="sourceLineNo">015</span> */<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>package com.google.common.util.concurrent;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>import static com.google.common.base.Preconditions.checkNotNull;<a name="line.19"></a>
<span class="sourceLineNo">020</span><a name="line.20"></a>
<span class="sourceLineNo">021</span>import java.util.concurrent.CancellationException;<a name="line.21"></a>
<span class="sourceLineNo">022</span>import java.util.concurrent.ExecutionException;<a name="line.22"></a>
<span class="sourceLineNo">023</span>import java.util.concurrent.Executor;<a name="line.23"></a>
<span class="sourceLineNo">024</span>import java.util.concurrent.TimeUnit;<a name="line.24"></a>
<span class="sourceLineNo">025</span>import java.util.concurrent.TimeoutException;<a name="line.25"></a>
<span class="sourceLineNo">026</span>import java.util.concurrent.locks.AbstractQueuedSynchronizer;<a name="line.26"></a>
<span class="sourceLineNo">027</span><a name="line.27"></a>
<span class="sourceLineNo">028</span>import javax.annotation.Nullable;<a name="line.28"></a>
<span class="sourceLineNo">029</span><a name="line.29"></a>
<span class="sourceLineNo">030</span>/**<a name="line.30"></a>
<span class="sourceLineNo">031</span> * An abstract implementation of the {@link ListenableFuture} interface. This<a name="line.31"></a>
<span class="sourceLineNo">032</span> * class is preferable to {@link java.util.concurrent.FutureTask} for two<a name="line.32"></a>
<span class="sourceLineNo">033</span> * reasons: It implements {@code ListenableFuture}, and it does not implement<a name="line.33"></a>
<span class="sourceLineNo">034</span> * {@code Runnable}. (If you want a {@code Runnable} implementation of {@code<a name="line.34"></a>
<span class="sourceLineNo">035</span> * ListenableFuture}, create a {@link ListenableFutureTask}, or submit your<a name="line.35"></a>
<span class="sourceLineNo">036</span> * tasks to a {@link ListeningExecutorService}.)<a name="line.36"></a>
<span class="sourceLineNo">037</span> *<a name="line.37"></a>
<span class="sourceLineNo">038</span> * &lt;p&gt;This class implements all methods in {@code ListenableFuture}.<a name="line.38"></a>
<span class="sourceLineNo">039</span> * Subclasses should provide a way to set the result of the computation through<a name="line.39"></a>
<span class="sourceLineNo">040</span> * the protected methods {@link #set(Object)} and<a name="line.40"></a>
<span class="sourceLineNo">041</span> * {@link #setException(Throwable)}. Subclasses may also override {@link<a name="line.41"></a>
<span class="sourceLineNo">042</span> * #interruptTask()}, which will be invoked automatically if a call to {@link<a name="line.42"></a>
<span class="sourceLineNo">043</span> * #cancel(boolean) cancel(true)} succeeds in canceling the future.<a name="line.43"></a>
<span class="sourceLineNo">044</span> *<a name="line.44"></a>
<span class="sourceLineNo">045</span> * &lt;p&gt;{@code AbstractFuture} uses an {@link AbstractQueuedSynchronizer} to deal<a name="line.45"></a>
<span class="sourceLineNo">046</span> * with concurrency issues and guarantee thread safety.<a name="line.46"></a>
<span class="sourceLineNo">047</span> *<a name="line.47"></a>
<span class="sourceLineNo">048</span> * &lt;p&gt;The state changing methods all return a boolean indicating success or<a name="line.48"></a>
<span class="sourceLineNo">049</span> * failure in changing the future's state.  Valid states are running,<a name="line.49"></a>
<span class="sourceLineNo">050</span> * completed, failed, or cancelled.<a name="line.50"></a>
<span class="sourceLineNo">051</span> *<a name="line.51"></a>
<span class="sourceLineNo">052</span> * &lt;p&gt;This class uses an {@link ExecutionList} to guarantee that all registered<a name="line.52"></a>
<span class="sourceLineNo">053</span> * listeners will be executed, either when the future finishes or, for listeners<a name="line.53"></a>
<span class="sourceLineNo">054</span> * that are added after the future completes, immediately.<a name="line.54"></a>
<span class="sourceLineNo">055</span> * {@code Runnable}-{@code Executor} pairs are stored in the execution list but<a name="line.55"></a>
<span class="sourceLineNo">056</span> * are not necessarily executed in the order in which they were added.  (If a<a name="line.56"></a>
<span class="sourceLineNo">057</span> * listener is added after the Future is complete, it will be executed<a name="line.57"></a>
<span class="sourceLineNo">058</span> * immediately, even if earlier listeners have not been executed. Additionally,<a name="line.58"></a>
<span class="sourceLineNo">059</span> * executors need not guarantee FIFO execution, or different listeners may run<a name="line.59"></a>
<span class="sourceLineNo">060</span> * in different executors.)<a name="line.60"></a>
<span class="sourceLineNo">061</span> *<a name="line.61"></a>
<span class="sourceLineNo">062</span> * @author Sven Mawson<a name="line.62"></a>
<span class="sourceLineNo">063</span> * @since 1.0<a name="line.63"></a>
<span class="sourceLineNo">064</span> */<a name="line.64"></a>
<span class="sourceLineNo">065</span>public abstract class AbstractFuture&lt;V&gt; implements ListenableFuture&lt;V&gt; {<a name="line.65"></a>
<span class="sourceLineNo">066</span><a name="line.66"></a>
<span class="sourceLineNo">067</span>  /** Synchronization control for AbstractFutures. */<a name="line.67"></a>
<span class="sourceLineNo">068</span>  private final Sync&lt;V&gt; sync = new Sync&lt;V&gt;();<a name="line.68"></a>
<span class="sourceLineNo">069</span><a name="line.69"></a>
<span class="sourceLineNo">070</span>  // The execution list to hold our executors.<a name="line.70"></a>
<span class="sourceLineNo">071</span>  private final ExecutionList executionList = new ExecutionList();<a name="line.71"></a>
<span class="sourceLineNo">072</span><a name="line.72"></a>
<span class="sourceLineNo">073</span>  /**<a name="line.73"></a>
<span class="sourceLineNo">074</span>   * Constructor for use by subclasses.<a name="line.74"></a>
<span class="sourceLineNo">075</span>   */<a name="line.75"></a>
<span class="sourceLineNo">076</span>  protected AbstractFuture() {}<a name="line.76"></a>
<span class="sourceLineNo">077</span><a name="line.77"></a>
<span class="sourceLineNo">078</span>  /*<a name="line.78"></a>
<span class="sourceLineNo">079</span>   * Improve the documentation of when InterruptedException is thrown. Our<a name="line.79"></a>
<span class="sourceLineNo">080</span>   * behavior matches the JDK's, but the JDK's documentation is misleading.<a name="line.80"></a>
<span class="sourceLineNo">081</span>   */<a name="line.81"></a>
<span class="sourceLineNo">082</span>  /**<a name="line.82"></a>
<span class="sourceLineNo">083</span>   * {@inheritDoc}<a name="line.83"></a>
<span class="sourceLineNo">084</span>   *<a name="line.84"></a>
<span class="sourceLineNo">085</span>   * &lt;p&gt;The default {@link AbstractFuture} implementation throws {@code<a name="line.85"></a>
<span class="sourceLineNo">086</span>   * InterruptedException} if the current thread is interrupted before or during<a name="line.86"></a>
<span class="sourceLineNo">087</span>   * the call, even if the value is already available.<a name="line.87"></a>
<span class="sourceLineNo">088</span>   *<a name="line.88"></a>
<span class="sourceLineNo">089</span>   * @throws InterruptedException if the current thread was interrupted before<a name="line.89"></a>
<span class="sourceLineNo">090</span>   *     or during the call (optional but recommended).<a name="line.90"></a>
<span class="sourceLineNo">091</span>   * @throws CancellationException {@inheritDoc}<a name="line.91"></a>
<span class="sourceLineNo">092</span>   */<a name="line.92"></a>
<span class="sourceLineNo">093</span>  @Override<a name="line.93"></a>
<span class="sourceLineNo">094</span>  public V get(long timeout, TimeUnit unit) throws InterruptedException,<a name="line.94"></a>
<span class="sourceLineNo">095</span>      TimeoutException, ExecutionException {<a name="line.95"></a>
<span class="sourceLineNo">096</span>    return sync.get(unit.toNanos(timeout));<a name="line.96"></a>
<span class="sourceLineNo">097</span>  }<a name="line.97"></a>
<span class="sourceLineNo">098</span><a name="line.98"></a>
<span class="sourceLineNo">099</span>  /*<a name="line.99"></a>
<span class="sourceLineNo">100</span>   * Improve the documentation of when InterruptedException is thrown. Our<a name="line.100"></a>
<span class="sourceLineNo">101</span>   * behavior matches the JDK's, but the JDK's documentation is misleading.<a name="line.101"></a>
<span class="sourceLineNo">102</span>   */<a name="line.102"></a>
<span class="sourceLineNo">103</span>  /**<a name="line.103"></a>
<span class="sourceLineNo">104</span>   * {@inheritDoc}<a name="line.104"></a>
<span class="sourceLineNo">105</span>   *<a name="line.105"></a>
<span class="sourceLineNo">106</span>   * &lt;p&gt;The default {@link AbstractFuture} implementation throws {@code<a name="line.106"></a>
<span class="sourceLineNo">107</span>   * InterruptedException} if the current thread is interrupted before or during<a name="line.107"></a>
<span class="sourceLineNo">108</span>   * the call, even if the value is already available.<a name="line.108"></a>
<span class="sourceLineNo">109</span>   *<a name="line.109"></a>
<span class="sourceLineNo">110</span>   * @throws InterruptedException if the current thread was interrupted before<a name="line.110"></a>
<span class="sourceLineNo">111</span>   *     or during the call (optional but recommended).<a name="line.111"></a>
<span class="sourceLineNo">112</span>   * @throws CancellationException {@inheritDoc}<a name="line.112"></a>
<span class="sourceLineNo">113</span>   */<a name="line.113"></a>
<span class="sourceLineNo">114</span>  @Override<a name="line.114"></a>
<span class="sourceLineNo">115</span>  public V get() throws InterruptedException, ExecutionException {<a name="line.115"></a>
<span class="sourceLineNo">116</span>    return sync.get();<a name="line.116"></a>
<span class="sourceLineNo">117</span>  }<a name="line.117"></a>
<span class="sourceLineNo">118</span><a name="line.118"></a>
<span class="sourceLineNo">119</span>  @Override<a name="line.119"></a>
<span class="sourceLineNo">120</span>  public boolean isDone() {<a name="line.120"></a>
<span class="sourceLineNo">121</span>    return sync.isDone();<a name="line.121"></a>
<span class="sourceLineNo">122</span>  }<a name="line.122"></a>
<span class="sourceLineNo">123</span><a name="line.123"></a>
<span class="sourceLineNo">124</span>  @Override<a name="line.124"></a>
<span class="sourceLineNo">125</span>  public boolean isCancelled() {<a name="line.125"></a>
<span class="sourceLineNo">126</span>    return sync.isCancelled();<a name="line.126"></a>
<span class="sourceLineNo">127</span>  }<a name="line.127"></a>
<span class="sourceLineNo">128</span><a name="line.128"></a>
<span class="sourceLineNo">129</span>  @Override<a name="line.129"></a>
<span class="sourceLineNo">130</span>  public boolean cancel(boolean mayInterruptIfRunning) {<a name="line.130"></a>
<span class="sourceLineNo">131</span>    if (!sync.cancel(mayInterruptIfRunning)) {<a name="line.131"></a>
<span class="sourceLineNo">132</span>      return false;<a name="line.132"></a>
<span class="sourceLineNo">133</span>    }<a name="line.133"></a>
<span class="sourceLineNo">134</span>    executionList.execute();<a name="line.134"></a>
<span class="sourceLineNo">135</span>    if (mayInterruptIfRunning) {<a name="line.135"></a>
<span class="sourceLineNo">136</span>      interruptTask();<a name="line.136"></a>
<span class="sourceLineNo">137</span>    }<a name="line.137"></a>
<span class="sourceLineNo">138</span>    return true;<a name="line.138"></a>
<span class="sourceLineNo">139</span>  }<a name="line.139"></a>
<span class="sourceLineNo">140</span><a name="line.140"></a>
<span class="sourceLineNo">141</span>  /**<a name="line.141"></a>
<span class="sourceLineNo">142</span>   * Subclasses can override this method to implement interruption of the<a name="line.142"></a>
<span class="sourceLineNo">143</span>   * future's computation. The method is invoked automatically by a successful<a name="line.143"></a>
<span class="sourceLineNo">144</span>   * call to {@link #cancel(boolean) cancel(true)}.<a name="line.144"></a>
<span class="sourceLineNo">145</span>   *<a name="line.145"></a>
<span class="sourceLineNo">146</span>   * &lt;p&gt;The default implementation does nothing.<a name="line.146"></a>
<span class="sourceLineNo">147</span>   *<a name="line.147"></a>
<span class="sourceLineNo">148</span>   * @since 10.0<a name="line.148"></a>
<span class="sourceLineNo">149</span>   */<a name="line.149"></a>
<span class="sourceLineNo">150</span>  protected void interruptTask() {<a name="line.150"></a>
<span class="sourceLineNo">151</span>  }<a name="line.151"></a>
<span class="sourceLineNo">152</span><a name="line.152"></a>
<span class="sourceLineNo">153</span>  /**<a name="line.153"></a>
<span class="sourceLineNo">154</span>   * Returns true if this future was cancelled with {@code<a name="line.154"></a>
<span class="sourceLineNo">155</span>   * mayInterruptIfRunning} set to {@code true}.<a name="line.155"></a>
<span class="sourceLineNo">156</span>   *<a name="line.156"></a>
<span class="sourceLineNo">157</span>   * @since 14.0<a name="line.157"></a>
<span class="sourceLineNo">158</span>   */<a name="line.158"></a>
<span class="sourceLineNo">159</span>  protected final boolean wasInterrupted() {<a name="line.159"></a>
<span class="sourceLineNo">160</span>    return sync.wasInterrupted();<a name="line.160"></a>
<span class="sourceLineNo">161</span>  }<a name="line.161"></a>
<span class="sourceLineNo">162</span><a name="line.162"></a>
<span class="sourceLineNo">163</span>  /**<a name="line.163"></a>
<span class="sourceLineNo">164</span>   * {@inheritDoc}<a name="line.164"></a>
<span class="sourceLineNo">165</span>   *<a name="line.165"></a>
<span class="sourceLineNo">166</span>   * @since 10.0<a name="line.166"></a>
<span class="sourceLineNo">167</span>   */<a name="line.167"></a>
<span class="sourceLineNo">168</span>  @Override<a name="line.168"></a>
<span class="sourceLineNo">169</span>  public void addListener(Runnable listener, Executor exec) {<a name="line.169"></a>
<span class="sourceLineNo">170</span>    executionList.add(listener, exec);<a name="line.170"></a>
<span class="sourceLineNo">171</span>  }<a name="line.171"></a>
<span class="sourceLineNo">172</span><a name="line.172"></a>
<span class="sourceLineNo">173</span>  /**<a name="line.173"></a>
<span class="sourceLineNo">174</span>   * Subclasses should invoke this method to set the result of the computation<a name="line.174"></a>
<span class="sourceLineNo">175</span>   * to {@code value}.  This will set the state of the future to<a name="line.175"></a>
<span class="sourceLineNo">176</span>   * {@link AbstractFuture.Sync#COMPLETED} and invoke the listeners if the<a name="line.176"></a>
<span class="sourceLineNo">177</span>   * state was successfully changed.<a name="line.177"></a>
<span class="sourceLineNo">178</span>   *<a name="line.178"></a>
<span class="sourceLineNo">179</span>   * @param value the value that was the result of the task.<a name="line.179"></a>
<span class="sourceLineNo">180</span>   * @return true if the state was successfully changed.<a name="line.180"></a>
<span class="sourceLineNo">181</span>   */<a name="line.181"></a>
<span class="sourceLineNo">182</span>  protected boolean set(@Nullable V value) {<a name="line.182"></a>
<span class="sourceLineNo">183</span>    boolean result = sync.set(value);<a name="line.183"></a>
<span class="sourceLineNo">184</span>    if (result) {<a name="line.184"></a>
<span class="sourceLineNo">185</span>      executionList.execute();<a name="line.185"></a>
<span class="sourceLineNo">186</span>    }<a name="line.186"></a>
<span class="sourceLineNo">187</span>    return result;<a name="line.187"></a>
<span class="sourceLineNo">188</span>  }<a name="line.188"></a>
<span class="sourceLineNo">189</span><a name="line.189"></a>
<span class="sourceLineNo">190</span>  /**<a name="line.190"></a>
<span class="sourceLineNo">191</span>   * Subclasses should invoke this method to set the result of the computation<a name="line.191"></a>
<span class="sourceLineNo">192</span>   * to an error, {@code throwable}.  This will set the state of the future to<a name="line.192"></a>
<span class="sourceLineNo">193</span>   * {@link AbstractFuture.Sync#COMPLETED} and invoke the listeners if the<a name="line.193"></a>
<span class="sourceLineNo">194</span>   * state was successfully changed.<a name="line.194"></a>
<span class="sourceLineNo">195</span>   *<a name="line.195"></a>
<span class="sourceLineNo">196</span>   * @param throwable the exception that the task failed with.<a name="line.196"></a>
<span class="sourceLineNo">197</span>   * @return true if the state was successfully changed.<a name="line.197"></a>
<span class="sourceLineNo">198</span>   * @throws Error if the throwable was an {@link Error}.<a name="line.198"></a>
<span class="sourceLineNo">199</span>   */<a name="line.199"></a>
<span class="sourceLineNo">200</span>  protected boolean setException(Throwable throwable) {<a name="line.200"></a>
<span class="sourceLineNo">201</span>    boolean result = sync.setException(checkNotNull(throwable));<a name="line.201"></a>
<span class="sourceLineNo">202</span>    if (result) {<a name="line.202"></a>
<span class="sourceLineNo">203</span>      executionList.execute();<a name="line.203"></a>
<span class="sourceLineNo">204</span>    }<a name="line.204"></a>
<span class="sourceLineNo">205</span><a name="line.205"></a>
<span class="sourceLineNo">206</span>    // If it's an Error, we want to make sure it reaches the top of the<a name="line.206"></a>
<span class="sourceLineNo">207</span>    // call stack, so we rethrow it.<a name="line.207"></a>
<span class="sourceLineNo">208</span>    if (throwable instanceof Error) {<a name="line.208"></a>
<span class="sourceLineNo">209</span>      throw (Error) throwable;<a name="line.209"></a>
<span class="sourceLineNo">210</span>    }<a name="line.210"></a>
<span class="sourceLineNo">211</span>    return result;<a name="line.211"></a>
<span class="sourceLineNo">212</span>  }<a name="line.212"></a>
<span class="sourceLineNo">213</span><a name="line.213"></a>
<span class="sourceLineNo">214</span>  /**<a name="line.214"></a>
<span class="sourceLineNo">215</span>   * &lt;p&gt;Following the contract of {@link AbstractQueuedSynchronizer} we create a<a name="line.215"></a>
<span class="sourceLineNo">216</span>   * private subclass to hold the synchronizer.  This synchronizer is used to<a name="line.216"></a>
<span class="sourceLineNo">217</span>   * implement the blocking and waiting calls as well as to handle state changes<a name="line.217"></a>
<span class="sourceLineNo">218</span>   * in a thread-safe manner.  The current state of the future is held in the<a name="line.218"></a>
<span class="sourceLineNo">219</span>   * Sync state, and the lock is released whenever the state changes to<a name="line.219"></a>
<span class="sourceLineNo">220</span>   * {@link #COMPLETED}, {@link #CANCELLED}, or {@link #INTERRUPTED}<a name="line.220"></a>
<span class="sourceLineNo">221</span>   *<a name="line.221"></a>
<span class="sourceLineNo">222</span>   * &lt;p&gt;To avoid races between threads doing release and acquire, we transition<a name="line.222"></a>
<span class="sourceLineNo">223</span>   * to the final state in two steps.  One thread will successfully CAS from<a name="line.223"></a>
<span class="sourceLineNo">224</span>   * RUNNING to COMPLETING, that thread will then set the result of the<a name="line.224"></a>
<span class="sourceLineNo">225</span>   * computation, and only then transition to COMPLETED, CANCELLED, or<a name="line.225"></a>
<span class="sourceLineNo">226</span>   * INTERRUPTED.<a name="line.226"></a>
<span class="sourceLineNo">227</span>   *<a name="line.227"></a>
<span class="sourceLineNo">228</span>   * &lt;p&gt;We don't use the integer argument passed between acquire methods so we<a name="line.228"></a>
<span class="sourceLineNo">229</span>   * pass around a -1 everywhere.<a name="line.229"></a>
<span class="sourceLineNo">230</span>   */<a name="line.230"></a>
<span class="sourceLineNo">231</span>  static final class Sync&lt;V&gt; extends AbstractQueuedSynchronizer {<a name="line.231"></a>
<span class="sourceLineNo">232</span><a name="line.232"></a>
<span class="sourceLineNo">233</span>    private static final long serialVersionUID = 0L;<a name="line.233"></a>
<span class="sourceLineNo">234</span><a name="line.234"></a>
<span class="sourceLineNo">235</span>    /* Valid states. */<a name="line.235"></a>
<span class="sourceLineNo">236</span>    static final int RUNNING = 0;<a name="line.236"></a>
<span class="sourceLineNo">237</span>    static final int COMPLETING = 1;<a name="line.237"></a>
<span class="sourceLineNo">238</span>    static final int COMPLETED = 2;<a name="line.238"></a>
<span class="sourceLineNo">239</span>    static final int CANCELLED = 4;<a name="line.239"></a>
<span class="sourceLineNo">240</span>    static final int INTERRUPTED = 8;<a name="line.240"></a>
<span class="sourceLineNo">241</span><a name="line.241"></a>
<span class="sourceLineNo">242</span>    private V value;<a name="line.242"></a>
<span class="sourceLineNo">243</span>    private Throwable exception;<a name="line.243"></a>
<span class="sourceLineNo">244</span><a name="line.244"></a>
<span class="sourceLineNo">245</span>    /*<a name="line.245"></a>
<span class="sourceLineNo">246</span>     * Acquisition succeeds if the future is done, otherwise it fails.<a name="line.246"></a>
<span class="sourceLineNo">247</span>     */<a name="line.247"></a>
<span class="sourceLineNo">248</span>    @Override<a name="line.248"></a>
<span class="sourceLineNo">249</span>    protected int tryAcquireShared(int ignored) {<a name="line.249"></a>
<span class="sourceLineNo">250</span>      if (isDone()) {<a name="line.250"></a>
<span class="sourceLineNo">251</span>        return 1;<a name="line.251"></a>
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<span class="sourceLineNo">399</span>    CancellationException exception = new CancellationException(message);<a name="line.399"></a>
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<span class="sourceLineNo">401</span>    return exception;<a name="line.401"></a>
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<span class="sourceLineNo">403</span>}<a name="line.403"></a>




























































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